The invention relates to a method of and apparatus for disaggregating particulate matter, and, more particularly, to a cutting-chipping mass removal system including an interconnected array of rotatable drums.
In the petroleum exploration and production industry it is often necessary to station men and equipment in relatively hostile environmental regions. In recent years the emphasis on oil production from the far north has necessitated development of new techniques for encountering formations of ice and the movements thereof which threaten the stability and/or position of equipment situated therearound.
In the Artic, large offshore regions are often covered by thick layers of ice. The recovery of minerals beneath these frozen waters requires the penetration of sections of ice for equipment installation. Similarly, once drilling platforms are installed and secured above a bottom mounted installation, it is important to keep the adjacent ice packs away from the moored platform structure. It is particularly necessary to have the capability of engaging an ice floe moving against the around such platforms so that the platform remains relatively stationary in conjunction with the borehole depending therefrom. The enormous mass of the moving ice in such regions has created a formidable problem fostering the need for effective means for expeditiously breaking up imposing ice layers.
Prior art ice removal systems have sought to provide cutters and chippers generally upon vertical or horizontal rotating drums, often operated in pairs, with axes of rotation being generally parallel. In Artic regions of platform operation, such cutters are often mounted on the bow of tugs which may circle drilling and production platforms to engage and cut the undesirable ice. This design and approach commonly facilitates a cutting-grinding action in the ice pack by "eating" away at the face of the abutting portions. Although effective in breaking up solidified, brittle masses, the basic cutting-grinding technique is antiquated. For example, a single rotating cutter will generally produce parallel spaced serrations with ridges therebetween in the ice. The serrations must be spaced close enough together to allow a second rotating cutter and/or blade, providing equally parallel serrations, to break up the ice ridges left from the first cutter. Because the ice is being struck, chipped and grooved in parallelism, the structural vulnerability of the ice ridges between serrations due to "shear" weakness is not addressed. Once a ridge is produced between two serrations in the face of a sheet of ice, it would take considerably less force to break and shatter the ridge by striking it at an oblique angle and thereby fracturing it in shear than it would to cut the ridge as a normal serration. With the "shear" approach, the ridges could actually be spaced further apart than is conventionally provided with normal cutters. In the same vein, it may be seen that it would take fewer teeth upon a drum to impart oblique angle blows to serrated ice ridges to accomplish the same degree of ice removal indicative of conventional parallel chipper systems.
It would be an advantage therefore, to overcome the disadvantages of prior art ice cutting and removal systems by providing means for effectively cutting serrations in masses of ice and the like and subsequently striking the ridges therebetween through oblique angles to break the ridges away. The method and apparatus of the present invention are provided for just such a purpose and for application involving other particulate matter such as coal. A triaxial array of cutter drums are provided, some of which are adapted to engage layers of ice and cut serrations therein at the same time other cutters engage the serrations which have just been cut and strike them at an oblique angle. The encountered ice, coal, or the like, may then be systematically cut, shattered and removed, rather than conventionally "chewed" upon. In this manner, less energy may be required to break up imposing ice layers or to cut through layers of coal, as the case may be. Similarly, mass removal may be effected in a more sophisticated and efficient fashion when particulate matter is involved.